3. Study Specimen Collection. Fecal samples and biopsies will be collected. Fecal samples will be assessed for fecal calprotectin and microbiota composition. This material will be snap frozen after collection. A total of 8 biopsies will be taken during sigmoidoscopy. For each type of analysis 2 biopsies will be taken from an area of disease between 15 and 20 cm from the anal verge. Biopsies will be used for analysis of mucosal host factors (qRT-PCR), mucosa-associated microbiota composition (16S pyrosequencing) and histology.